A new species of Loxosceles (Araneae, Sicariidae) from Tunisia

A new species of the spider genus Loxosceles, L. mrazig sp. n., found in Tunisia is described and illustrated. The male bulb shows a high degree of morphological similarity to that of L. gaucho from Brazil, but the pro- portions of the palpal segments and the general colouration of the body reveal significant differences between the two species. A distance analysis of the sequences of the mitochondrial gene cox1 reveals that the specimen from Tunisia shows high genetic distance from L. gaucho (more than 20%). The American species L. gaucho and L. laeta form a sister group to the Mediterranean representatives (L. rufescens and the Tunisian specimen). Taxonomy, Araneae, Loxosceles, new species, Tunisia

Ecological niche and phylogeography elucidate complex biogeographic patterns in Loxosceles rufescens (Araneae, Sicariidae) in the Mediterranean Basin

Background: Understanding the evolutionary history of morphologically cryptic species complexes is difficult, and made even more challenging when geographic distributions have been modified by human-mediated dispersal. This situation is common in the Mediterranean Basin where, aside from the environmental heterogeneity of the region, protracted human presence has obscured the biogeographic processes that shaped current diversity. Loxosceles rufescens (Araneae, Sicariidae) is an ideal example: native to the Mediterranean, the species has dispersed worldwide via cohabitation with humans. A previous study revealed considerable molecular diversity, suggesting cryptic species, but relationships among lineages did not correspond to geographic location. Results: Delimitation analyses on cytochrome c oxidase subunit I identified 11 different evolutionary lineages, presenting two contrasting phylogeographic patterns: (1) lineages with well-structured populations in Morocco and Iberia, and (2) lineages lacking geographic structure across the Mediterranean Basin. Dating analyses placed main diversification events in the Pleistocene, and multiple Pleistocene refugia, identified using ecological niche modeling (ENM), are compatible with allopatric differentiation of lineages. Human-mediated transportation appears to have complicated the current biogeography of this medically important and synanthropic spider. Conclusions: We integrated ecological niche models with phylogeographic analyses to elucidate the evolutionary history of L. rufescens in the Mediterranean Basin, with emphasis on the origins of mtDNA diversity. We found support for the hypothesis that northern Africa was the center of origin for L. rufescens, and that current genetic diversity originated in allopatry, likely promoted by successive glaciations during the Pleistocene. We corroborated the scenario of multiple refugia within the Mediterranean, principally in northern Africa, combining results from eight atmosphereocean general circulation models (AOGCMs) with two different refugium-delimitation methodologies. ENM results were useful for providing general views of putative refugia, with fine-scale details depending on the level of stringency applied for agreement among models

Diversitat del gènere Loxosceles Heineken & Lowe, 1832 a la Mediterrània i les Illes Canàries: sistemàtica, biogeografia i loxoscelisme

[cat] Les espècies d'aranyes del gènere Loxosceles són originàries de les zones temperades i tropicals d'Amèrica i d'Àfrica. La major part de les espècies tenen àrees de distribució relativament petites, tot i que existeixen algunes excepcions a aquest patró general, i algunes espècies amb hàbits antropòfils han estat transportades de forma passiva i introduïdes en diverses zones del planeta. Aquest és el cas, per exemple, de L. rufescens (Dufour 1820), l'única espècie descrita d'Europa. Actualment, la diversitat del gènere es concentra a Amèrica del Sud i del Nord, d'on s'han descrit la major part de les 107 espècies del gènere. L'objectiu principal d'aquesta tesi ha estat estudiar la diversitat del gènere Loxosceles a la Mediterrània, el Nord d'Àfrica i les Illes Canàries, i situar-la en un context filogenètic. L'intens mostreig de camp portat a terme per tota l'àrea d'estudi a posat al descobert l'existència d'una elevada diversitat. S'han identificat 11 llinatges mitocondrials dins de L. rufescens amb dos patrons filogeogràfics contrastats: (1) uns llinatges amb poblacions ben estructurades al Marroc i la Península Ibèrica, i (2) uns llinatges que manquen d'estructura geogràfica al llarg de la Mediterrània. Les estimes d'edats han situat la major part de diversificacions durant el Pleistocè, i la diferenciació al·lopàtrica dels llinatges és compatible amb els múltiples refugis Pleistocènics identificats amb la modelització de nínxol ecològics (ENM). Sembla que el transport indirecte pels humans ha complicat la biogeografia actual en aquesta espècie. En el cas de les Illes Canàries, les anàlisis filogenètiques han posat al descobert l'existència d'un clade ben recolzat endèmic de les Illes Canàries, format per set llinatges evolutius distribuïts de forma al·lopàtrica. La major part de dispersions entre Illes van succeir durant el Miocè superior. A més, també s'han trobat representants de l'espècie cosmopolita Loxosceles rufescens en l'arxipèlag. Sis dels llinatges pels quals es disposava de representants adults, s'han estudiat morfològicament i s'han descrit com a espècies nominals, quedant la diversitat de Loxosceles en les Illes Canàries amb una espècie endèmica de Fuerteventura i Lanzarote, dues de Gran Canària, dues més de Tenerife i una de La Gomera i El Hierro. Per tal d'aprofundir en la filogeografia de l'espècie endèmica de les illes i illots orientals, s'han desenvolupat set microsatèl·lits polimòrfics utilitzant les noves tecnologies de seqüenciació. Aquests nous marcadors han servit per a ressaltar la importància dels canvis en el nivell del mar i el vulcanisme en l'estructuració genètica d'aquesta espècie. Pel que fa a la diversitat de Loxosceles del Nord d'Àfrica, s'ha descrit una nova espècie de Loxosceles de Tunísia, L. mrazig, representant la segona espècie del gènere en la Conca Mediterrània. Tot i descriure's primerament d'una sola localitat, durant mostrejos posteriors s'han localitzat en diverses zones àrides del Nord d'Àfrica, des del Marroc fins a Israel. A més, l'estudi en profunditat a la regió del Souss-Massa del Marroc ha posat al descobert l'existència de diversos llinatges evolutius molt divergents molecularment i amb notables diferències morfològiques. L'estudi del verí de diferents llinatges de L. rufescens i de dues espècies de les Illes Canàries ha demostrat que existeixen diferències respecte a la composició principalment entre L. rufescens i les dues espècies canàries, que aquestes últimes expressen una diversitat menor de paràlegs de la família gènica SicTox, i que l'activitat esfingomielinasa D és en tots els llinatges i espècies estudiades tan elevada com en espècies americanes, les quals s'ha comprovat que poden provocar casos de loxoscelime.[eng] The spider genus Loxosceles Henieken and Lowe, 1832 is mainly distributed across the Americas and Africa. Most of the species show a narrow, circumscribed, distribution, although a few exceptions exist, for example L. rufescens (Dufour 1820), described from Europe. The aim of this thesis is to study the diversity of the genus Loxosceles in the Mediterranean Basin, North Africa and the Canary Islands, and to situate this diversity within a phylogenetic framework. The extensive sampling across the studied areas revealed the existence of hidden diversity. Using mitochondrial data, 11 different evolutionary lineages were identified within L. rufescens, presenting two contrasting phylogeographic patterns: (1) lineages with well-structured populations in Morocco and Iberia, and (2) lineages lacking geographic structure across the Mediterranean Basin. Dating analyses placed main diversification events in the Pleistocene, and multiple Pleistocene refugia, identified using ecological niche modelling (ENM), are compatible with allopatric differentiation of the lineages. Human-mediated transportation appears to have complicated the current biogeography of this medically important and synanthropic spider. This same species was found in the Canary Islands, where phylogenetic analyses revealed the existence of a well-supported clade formed exclusively by Canarian Loxosceles specimens, comprising seven allopatrically distributed evolutionary lineages. Morphological and molecular data confirmed the distinctiveness of six lineages and were described accordingly. Seven newly developed microsatellite markers were used to study the phylogeographic patterns of the species endemic to Fuerteventura and Lanzarote, and the study revealed the importance of sea-level changes and volcanism in shaping the genetic diversity in this species. Also, a new species of Loxosceles was described from Tunisia based on molecular and morphological data. Although this species was first described from a single locality, further sampling across North Africa expanded its distribution from Morocco to Israel. In the Souss-Massa region of Morocco, several highly divergent lineages were detected using molecular data and were shown to be also different morphologically. Using multiple approaches to study venom variation in selected species and lineages from the Mediterranean Basin and the Canary Islands, we found that SMase D activity, the key bioactive component of Loxosceles venom, is comparable to that of the American species that are confirmed to have medically relevant bites

A new species of Loxosceles (Araneae, Sicariidae) from Tunisia

A new species of the spider genus Loxosceles, L. mrazig sp. n., found in Tunisia is described and illustrated. The male bulb shows a high degree of morphological similarity to that of L. gaucho from Brazil, but the pro- portions of the palpal segments and the general colouration of the body reveal significant differences between the two species. A distance analysis of the sequences of the mitochondrial gene cox1 reveals that the specimen from Tunisia shows high genetic distance from L. gaucho (more than 20%). The American species L. gaucho and L. laeta form a sister group to the Mediterranean representatives (L. rufescens and the Tunisian specimen). Taxonomy, Araneae, Loxosceles, new species, Tunisia

Ecological niche and phylogeography elucidate complex biogeographic patterns in Loxosceles rufescens (Araneae, Sicariidae) in the Mediterranean Basin

Background: Understanding the evolutionary history of morphologically cryptic species complexes is difficult, and made even more challenging when geographic distributions have been modified by human-mediated dispersal. This situation is common in the Mediterranean Basin where, aside from the environmental heterogeneity of the region, protracted human presence has obscured the biogeographic processes that shaped current diversity. Loxosceles rufescens (Araneae, Sicariidae) is an ideal example: native to the Mediterranean, the species has dispersed worldwide via cohabitation with humans. A previous study revealed considerable molecular diversity, suggesting cryptic species, but relationships among lineages did not correspond to geographic location. Results: Delimitation analyses on cytochrome c oxidase subunit I identified 11 different evolutionary lineages, presenting two contrasting phylogeographic patterns: (1) lineages with well-structured populations in Morocco and Iberia, and (2) lineages lacking geographic structure across the Mediterranean Basin. Dating analyses placed main diversification events in the Pleistocene, and multiple Pleistocene refugia, identified using ecological niche modeling (ENM), are compatible with allopatric differentiation of lineages. Human-mediated transportation appears to have complicated the current biogeography of this medically important and synanthropic spider. Conclusions: We integrated ecological niche models with phylogeographic analyses to elucidate the evolutionary history of L. rufescens in the Mediterranean Basin, with emphasis on the origins of mtDNA diversity. We found support for the hypothesis that northern Africa was the center of origin for L. rufescens, and that current genetic diversity originated in allopatry, likely promoted by successive glaciations during the Pleistocene. We corroborated the scenario of multiple refugia within the Mediterranean, principally in northern Africa, combining results from eight atmosphereocean general circulation models (AOGCMs) with two different refugium-delimitation methodologies. ENM results were useful for providing general views of putative refugia, with fine-scale details depending on the level of stringency applied for agreement among models